1. FIELD OF THE INVENTION
The present invention relates to plastic shipping pallets for shipping large items, such as coils of metallic aluminum sheet, and more particularly to a plastic shipping pallet that includes an integral electrical conductor for discharging or dissipating to ground static electrical charges accumulated by the pallet or by the load thereon.
2. DESCRIPTION OF THE RELATED ART
Shipping pallets serving as base members to which large items are strapped or otherwise attached for shipment have been in use for a number of years. In the past such pallets were most often constructed of wood, usually because of the rigidity, weight, cost, and availability attendant with the use of that material. Recently, however, more and more of such shipping pallets are being made from molded plastic, because plastics are low in cost, because plastics can be easily and quickly molded to provide a pallet having virtually any desired size and configuration, because plastics pallets can be configured to be as strong and also lighter than wood pallets to support the same shape and weight items, and because plastics pallets are readily recyclable when they are damaged and no longer usable. The recyclability aspect is a significant factor affecting the total cost involved for plastics pallets, because damaged wood pallets are usually disposed of in landfills, a disposal method that is becoming increasingly more expensive.
Because plastics in general have a very low electrical conductivity, they are often used when insulating properties are desired. However, in a number of applications in which plastics are used their low conductivity results in a buildup of static electrical charge. Such static charges can attain significant voltages, of the order of up to about 1/2 million volts or so. Clearly, such charges on plastic shipping pallets are undesirable, because they can discharge and cause sparks in areas where combustible vapors or gases exist, and they cause uncomfortable shocks to personnel unloading or otherwise handling the items carried on pallets made from plastics.
Although plastic pallets are known, see, e.g., U.S. Pat. Nos. 4,103,857; 4,316,419; 4,966,083, and 5,178,075; there appear not to have been disclosed in any of those patents a plastic pallet that is capable of preventing the buildup on the pallet, and on the load attached thereto, of large charges of static electricity.
Accordingly, it is an object of the present invention to provide a plastic pallet including an integral conductive path for safely and simply discharging from the pallet and its load any accumulated large charges of static electricity.